Note that the debugger contains speedup modules, which use Cython and are generated with a few changes in the regular files to cythonize the files. The Cython speedups are available for CPython versions 2.7, 3.4 and 3.5.

On Windows the compiled Cython extensions are bundled to PyCharm.

On Linux and macOS, Cython extensions should be compiled manually in one in two possible ways:

by clicking the link that appears in the warning after the first debugger launch.

by running the command from the warning manually in the terminal. A separate Cython extension should be compiled for each version of Python interpreter.

If someone doesn't want to use Cython extensions for some reasons, the environment variable PYDEVD_USE_CYTHON=NO should be passed.